Cancer testis (CT) antigens are a class of tumour-associated antigens with expression normally restricted to germ cells in the testis, ovaries or trophoblast cells. These antigens are not usually expressed in adult somatic tissues. See, Simpson, et al., Nat. Rev. Cancer, 5 (8):615-625 (2005); Scanlan, et al., Immunol. Reviews, 188:22-32 (2002); Scanlan, et al., Canc. Immun., 4:1-15 (2004).
The gene regulation of CT antigens is disrupted in cancer patients, leading to the aberrant expression of these antigens in a wide variety of tumours. The first CT antigen to be identified, MAGE-1, was identified in the early 1990s by T-cell epitope cloning (van der Bruggen et al, 1991 Science 13; 254 (5038):1643-7; van der Bruggen et al, 1999 Science 254:1643-1647; Traversari, et al, 1992 Immunogenetics, 35 (3):145-152; and U.S. Pat. No. 5,342,774, incorporated by reference). Since then, serological expression cloning technique (SEREX) (Sahin, et al., Proc. Natl. Acad. Sci. USA, 92 (25):11810-11813 (1995) and U.S. Pat. No. 5,698,396), recombinant antigen expression on yeast surface (RAYS) (Mischo, et al., Canc. Immun., 3:5-16 (2003)) and differential mRNA expression analysis (Gure, et al., Int. J. Canc., 85 (5):726-732 (2000)) have led to the identification of approximately 90 CT antigens, and their number is expected to grow in the coming years. The immunogenicity of some CT antigens in cancer patients makes them an ideal target for the development of tumour vaccines.
NY-ESO-1. A cancer testis antigen currently of interest for use in cancer immunotherapy is NY-ESO-1. This antigen was first identified by SEREX in an oesophageal squamous cell carcinoma in the late 90's at the New York Branch of the Ludwig Institute for Cancer Research (Chen, et al., PNAS USA, 94 (5):1914-1918 (1997); and U.S. Pat. No. 5,804,381, incorporated by reference).
The protein NY-ESO-1 is 180 amino acids in length and can be described as being composed of three regions:
An N-terminal regionabout or approximately amino acids 1 to 70,A central regionabout or approximately amino acids 71 to 134,andA C-terminal regionabout or approximately amino acids 135 to 180.A collagen-like region comprises about or approximately or about amino acids 15 to 73 of the N-terminal region (see FIG. 1).
The protein NY-ESO-1 has been found in a wide variety of tumours, including but not limited to ovarian cancer, lung cancer, breast cancer, prostrate, oesophageal cancer, bladder cancer and in melanomas. (Nicholaou T, et al, Immunol Cell Biol. 2006 June; 84 (3):303-17 and Jungbluth, et al. 2001, Int. J. Canc., 92 (6):856-860). Spontaneous humoral and cellular immune responses against this antigen have been described in patients with NY-ESO-1-positive tumours, and a number of HLA (Human Leukocyte Antigen) class I- and II-restricted peptides have been identified (Jager, et al., 1998 J. Exp. Med., 187 (2):265-270; Yamaguchi, et al., 2004 Clin. Canc. Res., 10 (3):890-961; and Davis, et al., 2004 Proc. Natl. Acad. Sci. USA, 101 (29):10697-10702). Exemplary of the patent literature are U.S. Pat. Nos. 6,140,050; 6,251,603; 6,242,052; 6,274,145; 6,338,947; 6,417,165; 6,525,177; 6,605,711; 6,689,742; 6,723,832; 6,756,044; and 6,800,730, all incorporated by reference.
In a clinical trial, three partially overlapping NY-ESO-1-derived peptides with binding motifs to HLA-A2 (157-167, 157-165 and 155-163) have been used in a vaccine to treat twelve patients with metastatic NY-ESO-1 expressing tumours. This study demonstrated that synthetic NY-ESO-1 peptides can be administered safely and are capable of generating potentially beneficial T cell responses (Jager, et al., 2000 PNAS USA, 97 (22):12198-12203).
A number of MHC (major histocompatibility complex) class I and II epitopes in the protein have been identified by different groups see, for example, FIG. 1. These epitopes are merely representative of epitopes reported for the protein and the list in FIG. 1 is not exhaustive. Furthermore, at least one or more of the epitopes reported and/or listed in FIG. 1 have not been confirmed by experimentation. The collagen-like region in the N-terminal contains at least one MHC class I epitope referred to herein as A31. The central region comprises several MHC class 2 epitopes referred to herein as DR1, DR2, DR4, DR7 and DP4. This region also contains several MHC class I epitopes referred to herein as B35, B51, Cw3 and Cw6. The C-terminal is believed to contain at least two class II epitopes (DR4 and DP4) and one class I epitope (A2).
LAGE-1. A further cancer testis antigen, LAGE-1, has also been identified. Two LAGE-1 transcripts have been described, LAGE-1a and LAGE1b. LAGE-1b is incompletely spliced and codes for a putative protein of approximately 210 amino acids residues, while the LAGE-1a gene product contains 180 amino acid residues (Sun et al. Cancer Immunol Immunother 2006: 55: 644-652).
The N-terminal regions of the LAGE-1 and NY-ESO-1 proteins are highly conserved and are thought to have more than 97% identity. However, LAGE-1 differs from NY-ESO-1 in the central regions which are only 62% identical. The C-terminals of NY-ESO-1 and LAGE-1a are highly conserved (more than 97% identity). However, the C-terminal of LAGE-1b is longer and not conserved and is thought to have less than 50% identity with the same region in LAGE-1a/NY-ESO-1.
General information relating to these proteins is available from the LICR web site (see www.cancerimmunity.org/CTdatabase).